In order to describe more simply the apparatus, reference will be made to the decoration of profiled bars. As it is known, the decoration of metallic profiled bars, in particular for shutters and frames, previously painted with polymeric paint, is obtained by sublimation of colored inks having the property of subliming at a prefixes temperature and previously printed on a plastic or paper support, in order to form the desired decoration.
The decoration is transferred from the printed support to the substrate that is desired to be decorated by sublimation. Sublimation is a transition of a substance from the solid phase to the vapor phase, without passing through the liquid phase, by providing the substance with energy under the form of heat up to the temperature needed for such a process to take place.
Usually, the support, from which the decoration is transferred to the object to be decorated, is a film of plastic material, impermeable to air and capable of withstanding high temperatures, of about 250° C., without spoiling. Several systems are known that enable the sublimable decoration to be applied, which systems however can not disregard three phases of the decoration by sublimation:
1) placing into contact all the surfaces of the object that is desired to be decorated with the decorating film.
2) maintaining the decorating film adherent to the surfaces of the object, otherwise the vapor pressure of the sublimable inks would detach the decorating film from the surfaces of the object resulting in a transferred decoration of uncertain reading and definition.
3) heating the object wrapped in the decorating film, for example in a kiln, for raising the temperature of the decorating film wrapped about the object to be decorated to the temperature at which the inks sublime.
The known systems used for decorating the metallic profiled bars generally comprises two distinct apparatuses.
A first apparatus performs the construction of a wrapping, (generally tubular, the profiled bar being from six to seven meters long), formed with the decorating film wound around the profiled bar. The first apparatuses, with which the envelope or the wrapping of the profiled bar is formed, are so called wrapping machines, linear, tunnel, etc., normally used also in other production fields.
A second apparatus performs the sublimation of the decoration from the decorating film to the object.
An object of the invention is to improve the known apparatuses.
Another object is to resolve the problems arising in the phase 3) cited above that, in the light of the actual state of the art, constitutes an actual bottleneck for the purposes of increasing the production and the possible reduction of the costs.
A further object of the invention is providing a particular passing through kiln that enables to increase the daily productivity of decorated profiled bars, with respect to the systems currently known, passing from a number of 120-150 profiled bars per hour to more than 400.
Another object of the invention is that of providing a method for decorating objects by sublimation carried out by the apparatus.
FIG. 12 shows a first typology of kiln 30, presently known, which is supplied, usually, by means of one or more carriages comprising a frame 31, FIG. 13, whereon the profiled bars 33 are placed already wrapped into the film and separated from each other, at a prefixed pitch. Such carriages may support a number of profiled bars according to the number of openings 32, known, for sucking air, arranged in parallel rows at opposite ends of such carriages. The two open ends of the tubular enclosure made with the decorating film, inside which a profiled bar is longitudinally wrapped, are connected with suction ports 32, which are connected with a suction device such as a vacuum pump or a fan, not shown in figure.
Once the air between the film and the profiled bar has been sucked, the external atmospheric pressure causes the film to tightly adhere to the profiled bar, as required by the necessary cited condition 2). While the suction device is kept in function, the carriages are then introduced through the inlet 34 in the kiln 30 in order to reach the temperature necessary to cause the inks of the film to sublime and, thus, to transfer the decoration in the substrate of the surface of the profiled bars, previously painted, as known, with polymeric powders.
Once the sublimation of the inks has occurred the carriage 31 is extracted from the kiln in order for the profiled bars to be unloaded by the operators, and another, previously prepared carriage is introduced, giving rise to a new decoration cycle.
Another type of kiln 38, FIG. 14, called a passing through kiln, enables the profiled bars to be loaded step by step on closed loop chains 35 that form a supporting plane, said closed loop chains being driven by gear wheel 37. The upper portion of the chains 35 pass longitudinally through the kiln 38. The profiled bars, wrapped in the film, are laid on supports positioned on the plane formed by the conveyor chains 35 in the region E, being the ends of the film connected with suction ports 36, in order to create a degree of vacuum between the film and the profiled bar. Passing through the kiln from E to the exit F, the profiled bars are heated up to the sublimation temperature, whereby at the exit F of the kiln said profiled bars appear decorated and are unloaded by other operators.
From all that described above, it can be inferred that these technologies do not have the necessary industrial capability suitable for a reduction of the production costs, since their usage, due to the low productivity, requires the employment of manpower for at least three working turns per day in order to be economically convenient.
An object of the present invention is, then, to obviate the cited disadvantages of the state of the art, with a process and an apparatus that enable the restraints of the production cycle to be removed, the working turns to be reduced by combining the productivity of the three turns in only one turn, reducing, thus, both the costs of the manpower and the overall costs of the production.
An object of the present invention is an apparatus and a process for the continuous cycle decoration of profiled bars for shutters and frames, or other similar objects, by means of a film of plastic material, printed with the desired decoration with sublimable inks, that enable the disadvantages of the heretofore known technology to be removed.
As known in the present technology, after the profiled bar to be decorated has been prepared wrapped in the film and the other cited operations, said profiled bar has to be arranged on a carriage where more sucking stations exist, one for every profiled bar, comprising sucking ports for sucking air from inside the enclosure wrapped around the profiled bar. Such sucking ports are manually introduced by two operators, one operator for every end portion of the profiled bar, into the open ends of the enclosure, in order to cause the film of the enclosure to adhere to the profiled bar by means of suction of air from inside the enclosure until a degree of vacuum is reached. The sucking force is so as to oppose the force that will be developed due to the vapor pressure of the subliming inks, so that said film does not detach from the surface, preventing thus the decorative drawing from being diffused internally of the layer of the previously applied polymeric paint. Such suction is to be maintained also within the sublimation kiln in order to continuously suck the possible excess of vapors that could form. The time necessary for bringing the profiled bar to the sublimation temperature depends on the power of the kiln, the external surface of the profiled bar and its mass.
In these conditions the times for completing the sublimation are on average of the order of five, six minutes depending on the number of profiled bars to be decorated that has been introduced in the kiln, normally ten, twelve profiled bars. Since the profiled bars are six, seven meters long, working in an kiln of the type 38, FIG. 14 by loading a profiled bar at a time, sublimation times would be similar to the times described above since the kiln advancing speed is to be adjusted so as to follow the speeds of the loading operations, so as to obtain at most three, four decorated profiled bars per minute. The same production rate obtained also with carriage kilns.
Even increasing the number of the pre-wrapped profiled bars available, that is the number of the working wrapping machines for wrapping the decoration film around the profiled bars, or the number of personnel in charge, the described kilns are not capable of increasing their productivity due to the drawbacks imposed by their structure. It is apparent that in order to increase the productivity of such type of systems, the number of the kilns is necessary to be doubled or triplicated.
In these processes, a production of 100-120 decorated profiled bars per hour is considered acceptable.
The process and the apparatus of the invention can exceed these production rates, furthermore combining, the present daily production, accomplished in three working turns, in a single turn.
It is apparent that the apparatus of the invention has to be supplied by pre-wrapped profiled bars in a number sufficient for maintaining its very high productivity.